Impregnation with Salt Solutions

When a carrier is impregnated with a solution, where the catalyst deposits will depend on the rate of diffusion and the rate of adsorption on the carrier. Many studies have been made of Pt deposition from chloroplatinic acid (HgPtClg) with a variety of acids and salts as coim-pregnants. HCl results in uniform deposition of Pt. Citric or oxalic acid drive the Pt to the interior. HF coimpregnant produces an egg white profile. Photographs show such varied distributions in a single pellet. 

As stated above, a second route for the preparation of alkali-doped alkaline earth metal oxides is impregnation with aqueous solutions of alkali metal salts or hydroxides. As shown by Kijenski et al. (242), the resultant alkali metal-doped... 

Recently Mikae et al. (66) showed that NaY zeolite impregnated with NaCl solution can be used as a para selective catalyst for chlorination of chlorobenzene, which is indeed another example of zeolite modified advantageously by means of monolayer dispersion of salts. 

Particularly, Mo(VI)-Co(III) and Mo(VI)-Ni(II) containing species (here in CoMog and NiMo6 monolayer supported phases) have shown to be important precursors for HDS and HYD reactions [3,4], In this sense, it seems important to prepare and characterize the RhMoe species as both bulk and Y-AI2O3 supported phase (by equilibrium impregnation with aqueous solution of RhMoe ammonium salts) in order to analyze the catalytic behaviour. 

The filter was a porous alumino-silicate 29 mm OD and 13 mm ID tube (Goodfellow) with a porosity of 45% and a mean pore size of 90 pm. The BET specific surface area was 0.7 mVg. For the catalytic regeneration tests the filter was impregnated with aqueous solution of the salts used for the preparation of the catalyst 137AA, then dried at 393 K and calcined at 973 K overnight. In the uncatalysed regeneration the filter was used as received. 

In the case of strongly basic alkaloids, severe tailing may occur on silica gel plates because of the acidic properties of this adsorbent. Therefore, mobile phases containing bases like ammonia or diethyla-mine are widely used. Alternatively, TLC plates impregnated with basic solutions have been employed. For the detection of highly polar quaternary alkaloids and N-oxides, solvent systems consisting of methanol and aqueous salt solutions are useful. In Table 2 some widely used TLC systems are summarized. 

Ashless filter paper is impregnated with a solution containing 0.1 % of the ammonium salt of aurintricarboxylic acid (aluminon) and 1 % of ammonium acetate. One drop of an acid-aluminum solution is placed on the paper, developed over ammonia, and dried. A red lake is formed Idn. Limit 0.16 y Al). A number of other metal ions likewise form lakes with this reagent, but the products are decomposed by ammonia or ammonium carbonate. ... 

A porous catalyst pellet usually consists of a close packing of small porous catalyst particles of size 10—1000 A. The gases diffuse in the empty space between the particles as well as in the microscopic pores of the particles. The most important physical property of such a structure is the area per unit mass of the pellet, denoted by Sp. The values of Sp are in the range of 1 —1000m /g. The mass per unit of total volume Pp, and the void fraction Sp are also essential for the physical characterization of the catalyst. In many cases the porous pellets are impregnated with a solution of a metal salt and subsequently heated or treated chemically. The microscopic crystals of the metal or metal oxide deposited on the porous surface by this process give the catalyst its chemical reactivity. 

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